DC DC Converter Circuit

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Electronic system is designed to operate from a supply voltage, which is usually assumed to be constant. A voltage regulator provides this constant DC output voltage and contains circuitry that continuously holds the output voltage at the design value regardless of changes in load current or input voltage, assuming that the load current and input voltage are within the specified operating range for that regulator. In portable systems, the input voltage is often a battery, a DC voltage.

A DC-to-DC converter is a device that accepts a DC input voltage and produces a DC output voltage. Typically the output produced is at a different voltage level than the input. In addition, DC-to-DC converters are used to provide noise isolation, power bus regulation, etc. This is a summary of some of the popular DC-DC Converter Topologies

When the output voltage set point is less than the input voltage, such regulator is called a Buck converter. When the output voltage set point is higher, it is a Boost converter. A feedback input is necessary for the regulator to know the state of the output voltage so that it can be kept with in the tolerances required by the power supply design requirements. The converters control the output voltage to the specifications by comparing the output voltage (or current or both) to an internal reference.
In case of a Linear regulator the power is transferred continuously from Vin to Vout.
In case of a Switching regulator the power is transferred from Vin to Vout in bursts. There are two main types of the switching regulators – inductive and charge pump (capacitive).
Not every electronic system needs a regulator. The electronics in a typical system can operate within a narrow band (5% or 10%) around their rated voltage. The battery output voltage declines as the battery discharges. To prolong the usable life of the system, one could use electronics that operate at voltages toward the low end of the battery discharge. But, then the fresh battery voltage would far exceed the upper tolerance of the electronics. If the electronics were to be chosen for the upper end of battery voltage, then the battery would soon discharge to the lower tolerance of the electronics. One way to address this issue is wider range electronics, but this could be an expensive proposition. Another way is to use a regulator. If the battery voltage range is narrow (e.g. from NiCd cells), a low-dropout linear regulator may be suitable to produce a regulated lower output voltage. If the system voltage is higher than the battery voltage range, or within the range, then a switching regulator in a boost or buck-boost configuration can be used.

Simple DC to DC converter circuits:
6V to 12V DC-DC Converter with Transistors
This converter circuit can provide up to 800mA of 12V power from a 6V supply.

6V to 12V DC-DC Converter with IC
This step-up converter is intended for use in a car, has a 6V battery and won’t support a modern radio that needs 12V. The circuit described here converts 6V to 12V at 1A sustained load current.